U.S. Pat. No. 3,875,642 discloses a seaming apparatus utilizing three sets of rollers that is particularly suited for forming continuous seam structure along the side edges of panels having vertical side wall portions arranged parallel to one another and side connecting flanges that extend laterally out from the upper edge of vertical side wall portions.
U.S. Pat. No. 4,470,186 discloses a reversible seaming apparatus including a supporting frame on which there are rotatably mounted two sets of opposed seaming rollers, the sets being spaced from one another along the apparatus to successively engage and thereby seam the side edge portions of two adjacent panels together. One roller of each set is movable toward and away from the other roller of each set between a closely spaced seaming position and a laterally separated release position. A drive motor and drive train between the motor and rollers provide a direct positive drive for each roller when the rollers are in the seaming position. When the rollers are in their spread release position, the seamer may be lifted off any point along the adjacent edges which are being seamed. The ability to remove the seamer from any point along the edges is highly advantageous. However, this seamer disengages the rollers' drive gears when it is moved to its release position. Accordingly, the drive gears have to be reengaged when it is desired to return the seamer to its operating position. The gears may have difficulty reengaging if their teeth meet head on (i.e. end to end).